If I understand you, then an instance of Component B is embedded inside Component A, is that correct?
Conceptually, a component something like this:
Then A has no problems calling methods /functions in Component B. But, Component B cannot access methods / functions in Component A.
The [best] way to do this is to launch an event from ComponentB; something like this:
Then listen to it in Component and perform the function:
If you do it this way the two components are not tightly coupled and you optimize reuse.
But, in a pinch parent.myFunction() should work ( http://livedocs.adobe.com/flex/2/langref/mx/core/UIComponent.html#parent ). Did you try that? And what were the problems you had with it?